1. Field of the Invention
The present invention relates to an apparatus and method for negotiating settings between a base station and a mobile station in a wireless communication system. More particularly, the present invention relates to an apparatus and method for negotiating a sleep cycle setting between a base station and a mobile station.
2. Description of the Related Art
Extensive research is being conducted to provide various Quality of Service (QoS) features with a data rate of about 100 Mbps in the advanced fourth-generation (4G) communication systems. The 4 G communication systems are evolving to provide high mobility, high data rate transmission, and high QoS in Broadband Wireless Access (BWA) communication systems such as Local Area Network (LAN) systems and Metropolitan Area Network (MAN) systems, typical examples of which are identified in the Institute of Electrical and Electronics Engineers (IEEE) 802.16 system standards.
The addition/change/deletion of a service flow (i.e., a connection) in the IEEE 802.16m system is the same as a method of using DSx-REQ/RSP messages in the IEEE 802.16e system. That is, for adding a connection, a Mobile Station (MS) transmits a Dynamic Service Addition Request (DSA-REQ) message to a Base Station (BS) (in the event of an MS-initiated DSA), wherein the DSA-REQ message includes parameters necessary for adding the connection. On the other hand, the BS may transmit a DSA-REQ message to the MS (in the event of a BS-initiated DSA). Thereafter, in the event of an MS-initiated DSA, the BS transmits a Dynamic Service Addition Response (DSA-RSP) message to the MS in response to the DSA-REQ message received from the MS. On the other hand, in the event of a BS-initiated DSA, the MS may transmit a DSA-RSP message to the BS in response to the DSA-REQ message received from the BS.
Herein, the DSA-RSP message includes a confirmation code in response to the DSA-REQ message. As a response to the DSA-REQ message, the confirmation code represents an OK/success of a service connection request, or represents a failure of a service connection request and the reason for the failure. For example, if the BS transmits an ACKnowledgement (ACK) (OK/success) message in response to the DSA-REQ message from the MS, it may use ‘0’ as a confirmation code value of the DSA-RSP message. In this case, the DSA-RSP message includes a connection identifier (i.e., a multicast CID or a transport CID) and QoS parameters for the corresponding service. A method of using Dynamic Service Change (DSC)-REQ/RSP messages for changing a connection, or a method of using Dynamic Service Deletion (DSD)-REQ/RSP messages for deleting a connection is similar to the above method of using DSA-REQ/RSP messages for adding a connection, and thus a detailed description thereof will be omitted for conciseness.
The IEEE 802.16 system defines a sleep mode and an idle mode in order to minimize the power consumption of an MS. That is, if there is no communication traffic for an MS for a predetermined time (e.g., timer), the IEEE 802.16 system converts the state of the MS to a sleep mode or an idle mode. The MS may perform a power-down operation for a predetermined period by converting to the sleep mode or the idle mode. The MS does not perform a downlink (DL) channel monitoring operation in the power-down state, thus significantly reducing the power consumption. Also, the BS restricts available resources for the sleep-mode or idle-mode MS (unlike an active-mode MS), thereby increasing the network resource management efficiency.
The sleep mode defined in the IEEE 802.16m system is similar to the sleep mode defined in the IEEE 802.16e system, but it has the following unique characteristics.
First, in the IEEE 802.16 system, an MS and a BS define a sleep pattern operated in a sleep mode. The sleep pattern is called a power-saving class. The power-saving class includes a sleep interval and a listening interval. In the sleep interval, the MS performs a power-down operation. In the listening interval, the MS performs a channel monitoring operation while maintaining synchronization with the BS. In the IEEE 802.16e system, one MS may simultaneously have a plurality of different power-saving classes according to traffic characteristics. A connection made between the MS and the BS may correspond to one or more power-saving classes and the MS may simultaneously operate a plurality of power-saving classes in an overlapping manner. On the contrary, in the IEEE 802.16m system, one MS may have one power-saving class. In this case, if a different power-saving class is applied, it replaces the existing power-saving class.
In the IEEE 802.16 system, a listening window is interleaved between sleep windows. In the case of the sleep mode in the IEEE 802.16e system, the sleep window increases to twice the size of the existing sleep window in a situation where there is no traffic. On the other hand, the MS completely exits the sleep mode in a situation where there is traffic. On the contrary, in the case of the sleep mode in the IEEE 802.16m system, the concept of a sleep cycle (Sleep Cycle=Listening Window+Sleep Window) is introduced. In a negative-traffic situation, the sleep cycle increases to twice the size (the size of a sleep window increases because the size of a listening window is fixed to a default value). In a positive-traffic situation, the corresponding sleep cycle in the sleep mode is reset to the initial sleep cycle without exiting the sleep mode.
Meanwhile, in the IEEE 802.16m system, a conversion between a sleep mode and an active mode is performed by sleep mode-related management messages such as sleep (SLP)-REQ/RSP messages. That is, there is no conversion due to the presence of traffic. Herein, the MS transmits the SLP-REQ/RSP messages to the BS in order to convert from the active mode to the sleep mode, change sleep cycle settings in the sleep mode, or switch to the negotiated sleep cycle setting.
The QoS requirements change when the service flow (i.e., the connection) is added/changed/deleted. One sleep cycle pattern is applied in the sleep mode of the existing IEEE 802.16m system. Therefore, if the QoS requirements change, the sleep cycle pattern used up to that point may be unsuitable. Accordingly, the sleep cycle setting may have to be changed. In this case, by additional SLP-REQ/RSP messages, new sleep cycle settings may be applied, it may be switched to the existing sleep cycle setting, or the current sleep cycle setting may be changed. However, in addition to DSx-REQ/RSP message communication for addition/change/deletion of the service flow, this method requires additional SLP-REQ/RSP message communication in order to change the sleep cycle setting. Such an additional message communication process may cause significant overhead if the QoS requirements change frequently.